Best Practices for SAP BI using DB2 9 for z/OS - IBM Redbooks

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The ratio (ST04 statement cache “rows examined”/QDBSEL) is the number of rows examined for each row that satisfied the predicates. If this is high, it can be a sign of access path problems caused by predicate columns without indexes, or that DB2 is not able to use a filtering predicate early in the query to reduce the number of candidate rows. When a query is run with indexes that filter the result early and effectively, this ratio may be as low as 5 or 10. By itself, this ratio is not a reliable indicator of performance problems. For example, if a query contains a small table without a good index, the table may be repeatedly scanned and this ratio will be high, but the query may still run very quickly, since scanning a few dozen rows of a table in memory is fast. If you find a query that is slow, and where this ratio is high (for example, 100–500, or more), then use the ST04 Explain tool. 8.4 DB2 Visual Explain There is an alternative way to interpret the plan table output manually. You may want to consider using DB2 Visual Explain. It is a software tool that lets you view and analyze DB2 access paths graphically to facilitate your analysis and tuning of SQL queries or statements. The tool offers suggestions for improving the performance of your SQL queries or statements. You can change an SQL statement and dynamically explain it to see whether the access path is improved by the change. You can also use this tool to browse the current values of the subsystem parameters. DB2 Visual Explain makes Distributed Relational Database Architecture (DRDA) queries through a DB2 client on the (for example, Microsoft® Windows) workstation to get the information it needs. The subsystem parameter values are retrieved by calling a stored procedure on the host, which makes an IFI call to the appropriate DB2 trace record and returns them to the workstation. Basically, DB2 Visual Explain helps database administrators and application developers do the following: ► See the access path for a given SQL statement. ► Tune SQL statements for better performance. ► View the current values for subsystem parameters. 174 Best Practices for SAP BI using DB2 9 for z/OS
Figure 8-31, Figure 8-32 on page 176, and Figure 8-33 on page 177 show examples of DB2 Visual Explain windows. Figure 8-31 Visual Explain Plan Table - all rows displayed Chapter 8. Query and Load performance 175
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Best Practices for SAP BI using DB2
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Note: Before using this information
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4.4 Extended sparse index and in-me
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11.3 SAP BI database and InfoCube l
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viii Best Practices for SAP BI usin
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Trademarks The following terms are
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The team that wrote this IBM Redboo
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Thanks to these authors from the Pr
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► Send your comments in an e-mail
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1.1 Product overview The business w
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In general, database administrators
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► Horizontal growth is achieved b
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8 Best Practices for SAP BI using D
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2.1 BI architecture Figure 2-1 show
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New term Old term Analysis authoriz
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negative values means missing stati
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- When calculating database statist
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If you specify a partitioning schem
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Important: Never partition a PSA ta
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Figure 2-10 DPSIs versus NPSIs Figu
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Finally, Figure 2-12 explains which
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Figure 2-14 shows how the snowflake
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► Realignment This refers to the
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3.1 Base recommendations - SAP BI i
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the F- fact table, the E- fact tabl
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34 Best Practices for SAP BI using
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4.1 Dynamic index ANDing for star s
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Figure 4-2 and Figure 4-3 on page 3
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4.2.1 Processing RUNSTATS for BI ta
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RUNSTATS will then be called over t
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DSNU610I -DB2T 081 16:36:03.85 DSNU
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Often the single-value based freque
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Several things worth noting are:
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The unit of a value specified to MX
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condition, generated by SAP BI upon
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There is a separate IBM Redbooks pu
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5.1 Load PSA In this section we dis
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5.1.1 Load PSA To load data into th
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After the source system, the DataSo
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Note the available tabs (registers)
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Figure 5-8 shows the provided optio
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Figure 5-10 shows the following:
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The PSA table name is created autom
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5.1.4 PSA partitioning Partitioning
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An InfoCube, whether data target or
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6.1 Types of InfoCubes Data targets
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After selecting at least one time d
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6.2.1 Repartitioning implementation
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You will then be presented with a w
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From within the monitor you are abl
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Once your repartitioning process is
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Figure 6-14 is displayed once you h
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When you remodel an InfoProvider yo
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Figure 6-17 demonstrates how you wo
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At this step of the process you are
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6.3.2 Benefits of remodeling InfoPr
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6.4.3 Cumulative data versus non-cu
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Important: After the initial compre
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► Use DPSIs for the cube’s E- f
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7.1 Differences between DataStore a
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Figure 7-1 shows the initial status
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4. By selecting the Create button,
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Partitioning and clustering are bot
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7.4.2 Choosing and changing the clu
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7.4.4 Partitioning a DataStore obje
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From the ABAP Dictionary: Utility f
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Figure 7-9 DB2/390 Storage Attribut
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partitioning was used. The CREATE T
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, "/BIC/RECORDMODE" POSITION( 00289
Page 142 and 143: Upon completion of the job, you wil
Page 144 and 145: | "/BIC/DIVISION" VARGRAPHIC (00000
Page 146 and 147: | sql: | DELETE FROM DDSTORAGE | WH
Page 148 and 149: | "/BIC/CRMEM_VAL" DECIMAL (000017,
Page 150 and 151: | DDL time(___8): .........4 millis
Page 152 and 153: 134 Best Practices for SAP BI using
Page 154 and 155: 8.1 Troubleshooting general system
Page 156 and 157: You need to ascertain: ► Which us
Page 158 and 159: Further information about the subje
Page 160 and 161: 8.2 Analyzing load performance In t
Page 162 and 163: We use transaction ST03 → Expert
Page 164 and 165: Click the Details tab of the RSMO w
Page 166 and 167: Select the component of interest to
Page 168 and 169: Figure 8-11 All statistical records
Page 170 and 171: Figure 8-13 Single statistical reco
Page 172 and 173: Loading from a flat file You can av
Page 174 and 175: and right-click to select the Simul
Page 176 and 177: Note: You must activate the saving
Page 178 and 179: 5. In the right-hand panel of the w
Page 180 and 181: If your query has long run times th
Page 182 and 183: that the query runs against → Mai
Page 184 and 185: If the main component of query perf
Page 186 and 187: ► Display Statistics Data (to sho
Page 188 and 189: Select the appropriate button, ente
Page 190 and 191: Figure 8-29 Statement details To ch
Page 194 and 195: Figure 8-32 Visual Explain - SQL te
Page 196 and 197: 8.5 SAP Query Analysis Tool The SAP
Page 198 and 199: Display of sql access path SQL quer
Page 200 and 201: The access path is displayed hierar
Page 202 and 203: The table information tab shown in
Page 204 and 205: DB2 Plan Table Figure 8-42 DB2 plan
Page 206 and 207: Graphical view of each query block
Page 208 and 209: Now you see the graphical view of t
Page 210 and 211: 8.5.4 Example of using the query an
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Page 214 and 215: 9.1 The BIA architecture Figure 9-1
Page 216 and 217: Figure 9-2 BIA t-shirt sizing The B
Page 218 and 219: From the hardware side, the BIA is
Page 220 and 221: 9.7 Overview The improvement of the
Page 222 and 223: 10.1 SQL efficiency for DSO Queries
Page 224 and 225: The first join predicate is "/BIC/A
Page 226 and 227: Figure 10-5 Associate local predica
Page 228 and 229: Step 3 is repeated for each master
Page 230 and 231: Using the InfoCube query example in
Page 232 and 233: The first join predicate in Figure
Page 234 and 235: Thus, we have broken down the origi
Page 236 and 237: Figure 10-14 Comparing filtering Th
Page 238 and 239: AND "/BIC/AZOSASALE00"."PLANT" = "/
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10.4 Indexing of InfoCubes The defa
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11.1 Background To be more competit
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11.2.1 Hardware and software config
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11.2.2 Network infrastructure IBM S
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the chassis for blade-to-blade conn
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As part of the pre-benchmark planni
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11.4 Test case scenarios The goal o
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Figure 11-3 explains the data flow
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In addition, each cube, especially
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Measurement results Table 11-2 prov
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Figure 11-7 shows the average CPU u
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The number of queries per hour show
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Figure 11-10 shows that the average
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11.5.1 Recommendations for configur
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12.1 Terminology: BI objects and pr
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Metadata plays a fundamental role i
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12.3 Dataflow in SAP BI Data flow i
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12.4 Information access As previous
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Predecessor Successor WW Sales Euro
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An InfoCube in SAP BI can have up t
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12.8 Aggregates 4. The dimension ta
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The next example is an aggregate th
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For example, assume that different
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can be updated into InfoCubes or ot
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Figure 12-11 shows the steps that o
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Figure 12-12 on page 279 shows the
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The content, depicted in Figure 12-
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considerably more data records are
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The nodes stand for data sources, t
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values, hierarchies, hierarchy node
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BI SAP Query Connector A resource a
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Business Intelligence Cockpit Web-b
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processors in terms of macros that
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Crystal Reports Designer Design com
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Similar to the OLAP-standard term c
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P table Master data table for time-
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The process instance contains the m
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Relational Query Model An abstracti
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SAP Business Information Warehouse
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source object element Component of
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elements to be displayed in the Web
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Web application object catalog Web
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You insert one or more queries in t
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IT scenario The environment we used
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Checks under z/OS and DB2 We recomm
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To check that the SAPCL procedure w
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List of SAP BW OSS Notes Table C-1
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SAP BI on DB2 for z/OS 390016 BW Da
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Network configuration: static multi
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START CU091060 START CU0A1070 START
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Table name Average row length Total
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Table name Average row length Total
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Parameters BPK16K0 BPK16K1 VIRTUAL
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drwxr-xr-x 3 t11adm sapsys 2048 200
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Example D-6 shows a cube index crea
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B49/S_RTNSVAL 24 DECIMAL 17 2 N 4 N
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-rw-r--r-- 1 t11adm sapsys 2084482
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-rw-r--r-- 1 t11adm sapsys 547449 2
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Online resources These Web sites ar
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Help from SAP SAP Support and downl
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C Candidates for partiioning Data W
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M master data 155, 211, 258, 277 si
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star schema 265-266 also see InfoCu
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Best Practices for SAP BI using DB2
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